Sorry I wasn't around sooner but I've answered you about this in the KnownFolders thread (and for anyone else interested):
[VB6, Vista+] Code snippet: KnownFolders made easy with IKnownFolderManager

It's an oleexp project; and the mIID.bas addon that comes with it has all the FOLDERID_ GUIDs.

Or if you prefer, there's APIs, including SHGetKnownFolderPath (SHGetFolderPath now just wraps this function), to get the path of a KnownFolder from its GUID, but if you want to go path->GUID/object, you'll need the IKnownFolderManager.

The recycle bin is an odd item. It seems to have both a virtual representation and a hard path. So pidls can point to one or the other depending on the function.

The pidl structure is more complex than you'd think too; even with non-special folders, different methods of getting a pidl (ILCreateFromPath, IShellFolder for example) will return different values, but point to the same location.